A smiling man with short curly hair, wearing a checkered shirt, poses in front of a leafy green hedge.

Joshua Sussal, MD

Joshua Sussal has been in practice serving diverse populations of clients striving to provide mental health services to anyone in need. Dr. Sussal is Board Certified in Child and Adolescents as well as  General Psychiatry and has been a pioneer in neuromodulation through  technologies such as Transcranial Magnetic Stimulation.


  • General Psychiatry Residency at Stony Brook University, New York
  • Child and Adolescent Fellowship at Children’s National Medical Center, Washington, DC
  • Medical Degree from Ross University School of Medicine

He has worked within diverse and challenging settings. Some of these  settings include: the public mental health system, emergency room settings, inpatient facilities, partial hospitalizations, private practice and the judicial system.

He has also owned and operated his own mental health practice for  over 10 years allowing him to understand the impact of entering the  mental health system from the clients challenges in engaging and navigating to the clinicians obstacles in serving while balancing out the administration and management and oversight needed to coordinate to  be able to serve effectively but also efficiently.

Dr. Sussal uses his expertise in psychopharmacology and various  therapeutic modalities to meet each client where they are and to educate  and treat his clients where they want to be. He enjoys being privileged to be allowed to be part of each of his clients journeys and the trust and relationship building which goes along with them.

Dr. Sussal is also the Medical Director of the Greenbrook TMS Rockville, Greenbelt, and Frederick Centers, where he delivers Greenbrook TMS Therapy for patients with depression.

John Dahunsi, DNP, PMHNP-BC, MPH

Psychiatric Nurse Practitioner


  • Board Certified Registered Nurse Practitioner in Psychiatric Mental Health (PMHNP-BC)
  • Doctor of Nursing Practice (DNP)
  • Masters of Public Health (MPH)

John’s experience as a registered nurse for over ten years includes teaching, research, psychiatric inpatient units and crisis management. Seeing the overlay of trauma, mental health and substance abuse across all ages, identities, races and religions led him to want to help patients on a deeper level to make change and be present for their change on a more personal level. This was his motivation to go back and earn a Doctorate Degree to become a Psychiatric Nurse Practitioner. He has additional training in addictions to help serve as many patients as possible regardless of their diagnoses or comorbidities.

As a Board Certified Psychiatric Mental Health Nurse Practitioner who treats patients six years and older John enjoys working with individuals and their families to provide the best outcomes for patients mental health and physical health.

He is dedicated to understanding each individual’s life story because who we are shapes who we become. A deep understanding of who patients are allows him to provide tailored, high-quality, evidence based psychiatric therapies to help achieve the goals patients have set for themselves to achieve.

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Derek Chamberlain, LCPC

Clinical Director
Primary Therapist
Derek Chamberlain has been in the human services field for over 15 years. Derek is a Licensed Clinical Professional Counselor for the state of Nevada specializing in PTSD in adults and children. His specialties and scope of practice include individual, couples and  family therapy. 


  • Masters in mental health counseling with a strong concentration in addictions from Springfield college. CANS certification. TFCBT, DBT.

Military Experience

  • United States Marine Corps
  • United States Army 
  • Honorable Discharge

Training & Certifications

  • Certified DBT: for treatment of Borderline Personality Disorder, CBT, TFCBT (15 years) 
  • Individual / Group Counseling
  • Group Therapy
  • Crisis Intervention
  • Mental Health Counseling 
  • Child & Family Counseling
  • Addiction Counseling 
  • Motivational Interviewing 
  • Applied Behavior Analysis 
  • Crisis Management
  • Clinical Counseling
  • Behavioral Health
  • Approved clinical supervisor for the state of Nevada Marriage & Family Therapists. 

Derek’s life‘s journey and experiences have led him to where he is today. Along the way he has learned one of the most important things in therapy is “meeting the person where they are at”. Which leads to his philosophy about psychotherapy; Derek says, “therapy is about the relationship between the therapist and the client, there must be a mutual trust and understanding for any type of therapy to happen. I do not conform myself to any specific type of therapy. I use different modalities of therapy for different people “meeting them where they are “ in their journey. It is my belief as a therapist we must constantly be willing to learn new modalities new treatments and adapt ourselves to the diverse population we serve.”

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Carolyn Reidy

Business Manager
President & CEO, IOU Billing

Carolyn  was born and raised in the Hudson Valley of Upstate New York.  She  started her career in the mental health field in 1994 while working for  the Hudson Valley areas largest outpatient mental health facility. During her tenure she developed a strong knowledge of the mental health  field and kept many lasting relationships with key providers.  

Carolyn’s skills were recruited to the dental field that allowed her to manage and grow a successful practice  for the past 20 years along with her own medical billing business. Over time mental health providers branched off into their own business and  sought out Carolyn’s expertise to set up their private practices and  still utilize Carolyn business today. Some practitioners have been relying on Carolyn for over 20 years. As her medical billing business  has grown, her positive attitude has nurtured a string of relationships with health care providers and practitioners during this period of  time. She has met many challenges and difficulties of changing requirements with the same positive attitude.  

When you meet Carolyn, she is the same  welcoming person as the voice over the phone. Many of her longtime providers call her, “a fountain of information” when it comes to dealing  with medical and dental billing. Her dedication and growth of her  medical billing business allowed her to travel the world and branch off gain into another passion project travel agency which she has owned for  the past 5 years. 

During her free time she enjoys traveling, cooking and entertaining friends and family. She also enjoys  spending time with her two English bulldogs Winston and Bentley.

Carolyn Reidy established IOU BILLING to provide business consulting for small businesses. She provides the leadership and forward thinking that have got us this far. Her experience with medical & dental billing for over 26 years has allowed small business to grow and profi

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Denise Knight

Credentialing Specialist 

 IOU Credentialing Specialist
800-819-7570 ext. 101 

Denise has been working in the medical billing/credentialing field for almost 15 years and has extensive experience navigating the insurance companies for the enrollment and maintenance of our provider’s contracts. She has established relationships with insurance representatives throughout the years and is always happy to answer questions or concerns with regard to providers credentialing.

In her free time, Denise enjoys playing golf, spending time with her family and friends, camping and kayaking in the Adirondacks and traveling to the Outer Banks.

Lifespan Behavioral Health